adding a mechanism to black list instances
check for the black list
extracted the text file handling part
added a mechanism to only allow addition but not edits to existing text.

Adding 'de' to this list based on the discussion in https://groups.google.com/forum/#!topic/jenkinsci-dev/1fOaSLcy5aQ
attempted XSS injections
further restricting the values as I've seen someone testing XSS injection capability.